4). Let R and S be two relations on a set A. Then which is not correct?

A). R and S are transitive, then R u S is also transitive.

B). R and S are transitive, then R n S is also transitive.

C). R and S are reflexive, then R n S is also reflexive.

D). R and S are symmetric, then R U S is also symmetric

View Answer

Correct Answer: R and S are transitive, then R u S is also transitive.

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5). The group of beautiful girls is:

A). a null set

B). a finite set

C). a singleton set

D). not a set

View Answer

Correct Answer: not a set

Beautiful is relative term so, it is not well defined term. Therefore, it is not a set.

6). R is a relation over the set of real numbers and it is given by \( \Large nm \ge 0 \). Then R is:

A). symmetric and transitive

B). reflexive and symmetric

C). a partial order relation

D). an equivalence relation

View Answer

Correct Answer: an equivalence relation

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7). In a city of 55 students, the number of students studying different subjects are 23 in mathematics, 24 in physics, 19 in chemistry, 12 in mathematics and physics, 9 in mathematics and chemistry, 7 in physics and chemistry and 4 in all the three subjects. The number of students who have taken exactly one subject is: